The Effect Of MDF Deformation On Microstructure And Property Of Pure Magnesium

Multi-directional forging (MDF) is considered as a typical technics of severe plastic deformation (SPD) to fabricate bulk ultrafine grained materials. MDF was performed on pure magnesium to get fine-grained and well-performance material. Texts such as optical microscopy (OM) and scanning electronic microscopy (SEM) were used to investigate the microstructure, and tensile deformation at room temperature was used to get mechanical properties of Mg under different situations.MDF in constant temperature was performed on pure magnesium at 250°C, 350°C and 400°C. Fine-grained magnesium with average grain size of 14μm was gained; after 5 passes of forging at 350°C, the yield strength was 103.7MPa, and the ultimate tensile strength was 155.9MPa; after 6 passes of forging at 400°C, the elongation to failure reached 6.59%. The results from MDF in constant temperature showed: when the strain was fixed, as the increase of temperature, the average of grain size and the elongation to failure decreased, the yield strength increased and the ultimate tensile strength increased first then decreased; when the deformed temperature was fixed, as the stain increased, the average grain size decreased until a constant situation, the yield strength and the ultimate tensile strength increase and the elongation to failure increased first then decreased.Two different paths of MDF of decreasing temperature were performed on pure magnesium, the lowest deformation temperature reached 200°C, the fine-grained magnesium with the average grain size of 3.76μm was gained, and the yield strength was 101.8MPa; when deformed at 250°C, the ultimate tensile strength reached 152.3MPa, and the elongation to failure was 9.98%.The texture and the inhomogeneity of magnesium after MDF were also studied through EBSD and neutron diffraction. The texture {0002} was gained during the deformation, and the intensity decreased as the strain went. The deformation of MDF had the similar characters to free forging, the microstructure and the mechanical properties were inhomogeneous, but they got better with the strain increased.